This invention relates generally to the art of examining logic signals of an electronic circuit. In verifying the performance of a circuit or system under test (S.U.T.) it is often desirable to compare logic signals within the system to corresponding logic signals within a similar but known good system (K.G.S.) or circuit. A logic signal is acquired, in practice, by placing a probe contact on a conductive portion of the system. Such a contact point of a circuit is termed a "node". The logic signals at a plurality of nodes are generally desired to be acquired and examined in some manner such as by being displayed on a cathode ray tube.
One obstacle that often exists for comparing logic signals at the same node of two systems is that the systems may be driven by clock oscillators which differ in frequency. It is common for a system to have an R-C controlled timing frequency oscillator, the frequencies of the timing oscillators of different systems thus being subject to significant difference. Therefore, although the logic signals of a given system have a proper timing relationship to one another since they are based upon a common timing oscillator, it is difficult to compare logic signals between systems because the logic signals at any particular node will also differ by the difference in frequency of their respective timing oscillators.
Therefore, it is a principal object of the present invention to provide a technique for comparing logic signals of systems of the same type wherein compensation is automatically provided for different timing frequencies of the two systems.
It is another object of the present invention to provide a technique for comparing logic signals of two systems of the same type that is extremely convenient and fast for an operator that is comparing two systems.
It is yet another object of the present invention to provide an improved technique for acquiring and displaying logic signals from several nodes of a single system with the use of less complex equipment and with a corresponding increase in operator convenience.